Ovens in conventional domestic electric ranges are generally equipped with high wattage heating elements so that the oven warm-up time is short. Typically a rate of temperature rise of one degree per second is not uncommon. Under such warm-up conditions the rate of response of the oven temperature sensor to this sudden increase in temperature must be sufficiently rapid to prevent an excessive first cycle overshoot in the oven temperature.
Presently, when using a conventional resistance sensor having a heating time constant of 1.5 minutes in a typical domestic oven, an overshoot of 100.degree. F. or more during warm-up is not unusual. This overheating represents a waste of expensive electrical energy. While resistance sensors having an adequately fast response are presently available they do not have sufficient electrical insulation to be directly connected in a line voltage circuit. A low voltage transformer with an isolated secondary is required to use such probes. Even then isolation between the low voltage control circuit and the oven heater power circuit must also be provided.
Experience has shown the inclusion of an adequate thickness of high temperature electrical insulation material around a typical bobbin wound resistance element so that it may be used in the line voltage circuit creates too much thermal mass in the sensor for it to respond with adequate speed to increasing oven temperatures and thus avoid overshooting.